Setting the Baseline

3.1 The scoping process and definition of ‘zone of influence’ (Chapter 2) should result in an agreed schedule of activities to inform the impact assessment process. Desk studies completed as part of the scoping process, or carried out as a first phase in the setting the baseline will identify those areas requiring additional data collection.

3.2 Impacts on part of a habitat or population/assemblage may have implications for the whole habitat or population and the study limits should be adjusted accordingly. Furthermore, the vulnerability of different habitats and species may vary greatly, depending on the project, and consequently the spatial scope of studies should be sufficiently flexible to accommodate differing needs.

3.3 The conditions that define the baseline need to be carefully considered. This is because the baseline may differ from conditions that exist at the time an assessment is made (see Box 8 below). In order to determine this, it is necessary to try to predict any changes that will alter conditions prior to the start of the proposed construction and subsequent to it (see Box 9 Chapter 5). There may be overlap between establishing the baseline in this situation and considering cumulative impacts that might be expected (see Chapter 5). This should be determined through discussion between relevant stakeholders in the EcIA process.

3.4 Variation in a population over time, in preference to a single year’s data should be presented if sufficient data are available. If sufficient data are not available a view should be taken as to whether such data should be collected based on collective experience from similar projects. It is important to design such data collection within a robust statistical framework to ensure the data are fit for purpose, for example that sufficient data are collected to ensure that inferences can be made with a sufficient degree of statistical confidence.

3.5 Where the zone of influence potentially extends over a large area, and particularly where there is limited existing information, it may be useful to undertake a preliminary characterisation at a broad scale to inform the scope, boundaries and design of subsequent detailed baseline surveys. Characterisation could incorporate desk-top analysis, modelling and data collection (perhaps at a lower resolution than might subsequently be required to inform EcIA itself).

3.6 Data needs should also be informed by consideration of the potential for cumulative and in-combination effects. Developing a strategy for the assessment of these potential effects requires consideration of both the spatial scale and resolution of data collection required to provide an appropriate baseline. For regional clustered developments, such as marine aggregates and offshore wind, processes have been developed in Britain (Regional Environmental Assessment23 and Zone Appraisal and Planning24) that are intended to facilitate a structured analysis of the potential for cumulative and in-combination effects and the design of appropriate baseline data collection strategies. Guidance is available for both of these processes and should be followed or adapted as/where appropriate to the project.

Informing the Baseline

3.7 Where available, professionally accredited or published scientific studies should be used to establish the likely spatial and temporal limits of ecological impacts for specific activities and to justify decisions made at the scoping stage. Assumptions made based on such studies should be recorded.

3.8 Study boundaries should be drawn to include and distinguish all areas that are affected, either directly or indirectly. For example, with dredging, the area of impact could extend beyond the dredged area to include areas of sediment re-deposition or erosion. If indirect effects are also taken into account (e.g. the effects of displaced individuals on the occupancy of alternative habitat), then the ‘zone of influence’ could be considerably larger. Box 8 provides an example of factors to consider when defining a zone of influence.

Box 8: Setting the Baseline

Example illustrating factors to consider when defining the zone of influence

Where a new port is proposed, it is important to ensure that there is sufficient knowledge of the total environment that may be affected, the ‘zone of influence’. This can include:

numbers and diversity of breeding birds such as terns and ringed plovers and their past/present breeding success;

distribution and numbers of waterfowl during spring and autumn passages, or during winter, (using affected site and within the water body as a whole);

locations of major high tide roosts and loafing areas for waterfowl;

fish assemblages including migratory species and the timing of movement of larvae, juveniles and adults;

benthic species in the intertidal and subtidal zones, particularly protected and/or endangered species, or commercially important species e.g. some shellfish;

hydrodynamic modelling of key factors such as sediment transport, wave direction and magnitude, water current direction and speed in order to predict the extent of the impact on the surrounding environment;

historic evolution of estuarine morphology, when available;

the extent of inter-tidal and subtidal biotopes, including saltmarshes, soft sediment communities, rocky and biogenic reefs; and

tidal propagation, suspended sediment load and bathymetry.

These data are needed to set the context and to provide a baseline for evaluation of impacts such as displacement, modification or loss of critical habitats for key species, e.g. feeding areas for waterfowl, fish and benthic species; loss of extent of roosts, refuge and breeding areas; geomorphological evolution and impacts, and validation of predictive models.

3.9 Comprehensive surveys of habitats and/or populations/assemblages within the zone of influence should be undertaken as appropriate. It is recommended that habitats and species should be classified in accordance with the Marine Habitat Classification for Britain and Ireland25, 26. Surveys should, as far as practicable, use established methodologies (e.g. those of the JNCC and MNCR27 or others as recommended by SNCOs). Any habitat surveys should identify the main habitat types or biotopes (the physical habitat with its biological communities) that may be affected by the project and provide a documented basis for determining the scope of more detailed surveys.

3.10 Where assessments have a wide geographic coverage (e.g. for proposed offshore windfarms) the use of remote sensing techniques (including aerial surveys, aerial photography and satellite imagery) should be used where available. These can provide insights into spatial relationships, so that the impact assessment identifies ecological distributions, processes and interactions at appropriate scales. Consideration needs to be given to the appropriate scale and spatial resolution of data collection activities in light of the regional scale effects of these types of development activities.

3.11 Where it is necessary to gather data on specific areas or issues identified through scoping, standard survey methods28 should be used wherever appropriate. This will allow results to be compared with those arising from other investigations. Details of how and where methods have been tailored to meet the needs of the study should be included. If the method used varies from accepted good practice this should be explained and the effect on the reliability of the results discussed. Limitations to the interpretation of information utilised in reports or advice should also be provided.

3.12 Baseline surveys must also take account of possible impacts identified through scoping and be designed accordingly. For example, developments for which acoustic disturbance has been identified as likely should require the baseline to include definition of the existing ‘soundscape’ of the zone of influence.

3.13 Results of baseline studies should be used to build a picture of ecological features, resources and ecosystem processes, and those processes supporting ecological components within the zone of influence, for consideration in the Chapter 4 on Determining Value and Chapter 5 on Impact Assessment.